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29 views

Help finding the net electric charge flux! [closed]

If electric charge flows with a current density vector function of $$ \mathbf J=\frac7R\hat{R}\,\,\,\,\,{[\rm A\,m^{-2}]} $$ find the net electric charge flux (i.e., the net current) flowing through ...
0
votes
2answers
30 views

Finding out time $t$ when a particle is more likely to be on the right half than the left half of the box [closed]

Question: A particle with mass $m$ is trapped in a box of length $L$. At $t=0$, it has wavefunction as following: $$\psi(x,t=0)=\sqrt[]{\frac2{41\pi}}(3u_1(x)+4u_2(x))$$ where $u_1(x)$ and ...
3
votes
1answer
68 views

Yang-Mills constraints and Poisson brackets

Let's have constraints for Yang-Mills theory: $$ \varphi_{a} = \partial_{i}\pi^{i}_{a} - f_{abc}\pi^{b}_{i}A^{c}_{i}. $$ I have read the statement that $$ \tag 1 [\varphi_{a}(\mathbf x), ...
0
votes
2answers
101 views

combination of cells

There are m*n identical cells of emf E and internal resistance r connected in parallel rows. This combination of cells is connected across an external resistance R. For what arrangement of the ...
0
votes
1answer
64 views

Are the Pauli matrices closed under commutation?

I tried to make a group multiplication table for the Pauli matrices, but I keep getting multiples in front of the elements. What am I doing wrong? I thought the Pauli matrices formed a group that was ...
-2
votes
1answer
21 views

Linearization of equation of oscillatory motion [closed]

I need to linearize this function using Taylor series $$ \frac{3 A P_0 L}{2 x_{eq}} - \frac{A P_0 L}{2\left(L-x_{eq}\right)} $$ times $(X-X_{eq})$. Order of 1, just function which is zero because $X$ ...
2
votes
1answer
75 views

Normalization of a wavefunction that's superposition of two unknown energy eigenfunctions

Question:$$\psi(x)=A(3u_1(x)+4u_2(x))$$where $u_1(x)$ and $u_2(x)$ are energy eigenfunctions. How to normalize function $\psi(x)$? My intuitive solution: I got ...
0
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0answers
10 views

Find the SHM time interval [closed]

Parts i) and ii) I can solve. But for part iii) I can't do, as I don't know which equation describes the SHM motion? Is it $y=0.5sin(1.2t)$ or $y=0.5cos(1.2t)$ or $x=0.5sin(1.2t)+2.5$? I thought ...
1
vote
0answers
36 views

OPE of fermionic field bosonization in string theory, in Polchinski 10.3.12

In Polchinski's String Theory Vol. 2, equations 10.3.12 are $$e^{iH(z)}e^{-iH(-z)}~=~\frac{1}{2z}+i\partial H(0)+2zT_B^H(0)+O(z^2)\tag{10.3.12a}$$ ...
0
votes
0answers
73 views

How to prove $\hat{p}|x\rangle=i\hbar\frac{\partial}{\partial x}|x\rangle$,using $[\hat{x},\hat{p}]=i\hbar$? [duplicate]

How to prove $$\hat{p}|x\rangle=i\hbar\frac{\partial}{\partial x}|x\rangle,$$ using $$[\hat{x},\hat{p}]=i\hbar~?$$ The question seems to be uncomplete because for any $f(x)$ ...
-2
votes
1answer
24 views

Accelerating Tetrahedron [closed]

Four identical spheres are in contact with each other and form a tetrahedron. If acceleration of the top sphere is $a$, find the acceleration of the spheres on ground.
0
votes
1answer
30 views

Introductory Quantum, trouble with this boundary condition and potential

Working on problem 2.40 from Griffiths but can't seem to understand the first boundary condition. We are given the potential $V(x) = \left\{\begin{matrix} \infty & x < 0\\ ...
0
votes
0answers
19 views

What is the energy-momentum four vector of the particle? [closed]

An particle with mass $0.511~\text{MeV/c^2}$ is travelling $0.4c$ in the x-direction. What is the energy-momentum four vector of the particle (E/c, $p_x$, $p_y$, $p_z$)? A ship moving in the ...
0
votes
0answers
23 views

Two protons moving at a relativistic velocity collide? [closed]

Two protons moving at a relativistic velocity (the same for both protons) collide head-on. The collision results in a, unstable, single particle with mass 130GeV/c^2. What was the gamma factor and ...
2
votes
2answers
280 views

About partially polarized light and the degree of polariztion

When I was taking Optics course, I found there were several questions about polarization of light. I use the textbook of Hecht. It seems that the definition of degree of polarization may be not so ...
1
vote
2answers
35 views

Determining bound states for delta function potential

I'm working on a problem out of Griffith's Intro to QM 2nd Ed. and it's asking to find the bound states for for the potential $V(x)=-\alpha[\delta(x+a)+\delta(x-a)]$ This is what I'm doing so far: ...
1
vote
0answers
32 views

Change of Basis For Pauli Matrix From Z Diagonal to X Diagonal Basis

I want to find a matrix such that it takes a spin z ket in the z basis, $$ \lvert S_z + \rangle_z $$ and operates on it, giving me a spin z ket in the x basis, $$ U \lvert S_z + \rangle_z = ...
1
vote
1answer
49 views

2 simple Generators = Im lost (intensity) [closed]

What happens? we have 2 Generators and 2 intensities, when I2 and I3 come together (they have opposite sides ) what happens? I tried writing down the voltage relations but I'm stuck because I don't ...
0
votes
1answer
56 views

Center of mass after explosion [closed]

How he treated the center of mass as if it is still in the same place , is not it supposed to change after explosion ? and is not explosion destroying the closed system? i mean it represents and ...
0
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2answers
61 views

How to find the amplitude of magnetic field of this plane wave

Because my previous question was short and confusing, it was put on hold. This is my new question, which getes straight to the point. I have an electromagnetic plane wave which has wavelength $λ$ = ...
0
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3answers
64 views

Finding the Direction when resolving a Vector

When you are finding the resultant of a vector I understand that to find the magnitude you use Pythagorean Theorem and I understand that to find the direction you are going to use $\tan^{-1}$ (or ...
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0answers
26 views
1
vote
1answer
147 views

photon polarization, uncertainty in Energy

A beam of red light is sent along the $z$ axis through a polaroid filter that passes only $x$ polarized light. The beam is initially polarized at $30$°, and the total energy is $10$ Joules. Estimate ...
1
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0answers
23 views

Electric field of Symmetric Parts [closed]

So I'm preparing for a test and one thing that I haven't seen examples of, but know is possible is using Gauss's Law on objects that have symmetric parts. I made up the following question: Find ...
3
votes
1answer
40 views

Kraus operator rank

All quantum operations $\mathcal{E}$ on a system of Hilbert space dimension $\mathcal{d}$ can be generated by an operator-sum representation containing at most $\mathcal{d^2}$ elements. Extending ...
0
votes
1answer
18 views

Final velocity of a spring [closed]

I need to calculate the velocity of an object when it is thrown by a spring; we have to calculate the velocity from $U=\frac 12 kx^2$. Now I know that $U=L=F\cdot S$ and $S=\frac{v_f^2-v_0^2}{2a}$. ...
0
votes
0answers
32 views

Force, Mass and Acceleration [closed]

I was looking at the following question and was just wondering if it was as simple as it sounded. A man is in a car and starts to accelerate at $5ms^{-2}$. (a) If the gentleman weighs 75kg, ...
0
votes
1answer
38 views

Plancks law of blackbody radiation

I am going to plot this curve with wave length: $$ I(f)df = \frac{2 \pi h}{ c^{2} } \cdot f^{3} \cdot \frac{1}{ e^{ \frac{h f}{kT}-1 } } df $$ converting: $$ I( \lambda )d \lambda = \frac{2 ...
1
vote
1answer
2k views

Minimum height of mirror required to view image

I wanted to know the minimum height of mirror required to be able to view a complete image of a person. I considered the following setup: $HF$ is the person in question. $H$ denotes the head, $F$ ...
0
votes
0answers
29 views

Application of Snell's Law || Basic Optics [closed]

As shown in the diagram the setup consists of a source and a detector in a 2 layered medium-the interface being inclined to the horizontal.Will the travel times for both cases(source to detector and ...
0
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1answer
46 views

Equation for Terminal Velocity on an inclined plane and the time it takes to reach it

Now I'm doing a research on the matter similar to this thread : Terminal Velocity of identical shape/size objects which is very self explanatory and very helpful. However in my case, the objects will ...
-2
votes
0answers
20 views

Physics Homework help [closed]

If a curve with a radius of 80m is properly banked for a car traveling 62km/h , what must be the coefficient of static friction for a car not to skid when traveling at 92km/h ?
-1
votes
1answer
17 views

Optics, finding the acceleration of images [closed]

the acceleration of both the blocks of mass m will be g, hence the acceleration of the images will be 2g. acceleration of the two images w.r.t. each other will be 2g + 2g = 4g but the answer is ...
0
votes
0answers
12 views

Determining speed of transverse wave [closed]

A transverse wave on a string, given angular frequency $\omega$, wave number $k$ and max displacement from equilibrium $A$. Determine the speed of the wave along the string. ATTEMPT $ v = { \omega ...
4
votes
2answers
183 views

What's wrong with my derivation for the spring constant? [duplicate]

An $8.00\ \mathrm{kg}$ stone at rest on a spring. The spring is compressed $10.0\ \mathrm{cm}$ by the stone. What is the spring constant? I used conservation of energy to solve this problem. The ...
2
votes
0answers
107 views

Help with the inverse of a matrix [closed]

In some paper I have been reading there is a matrix $M_{ij} = g_{ij} + \epsilon_{ijk}y_k$. In the RHS $g$ is the metric of some manifold and $y_i = b_i + v_i$ where $b_{ij} = \epsilon_{ijk} b_k$ and ...
1
vote
1answer
121 views

Confused about elasticity and collisions

I was solving the following problem and the explanation to it confused me. There are two objects with mass $m$ and $M$, respectively. The object with mass $m$ has a velocity of $\sqrt{2gl}$ and ...
0
votes
1answer
46 views

Speed, Velocity and Acceleration

How do you calculate an equation that asks to calculate the final velocity without time being given? But with distance being given...
0
votes
0answers
14 views

Calculating entropy [duplicate]

Suppose 30 gram of metal Gallium melts at 36 °C. The specific heat of fusion is 80.3 kJ/kg and the melting temperature is 29.9 °C. Explain if the melting of the Gallium in this process is ...
-1
votes
0answers
30 views

Determine change in entropy - Please verify [closed]

Suppose 30 gram of metal gallium melts at 36°C. The melting temperature is 29.9 °C and specific heat of fusion is 80.3 kJ/kg. Explain if the melting of the gallium in this process is reversible or ...
0
votes
1answer
34 views

Transformation to a uniformly rotating frame

I'm midway through a problem at the beginning of a GR course, my question is simply this: If $$ x=x'\cos\Omega t-y'\sin\Omega t $$ where $x'$ and $y'$ indicate the rotated frame of reference. What ...
0
votes
0answers
30 views

Vector of electric field

I have a triangle whose points are in $A(0,0,0)$, $B(a,0,0)$ and $C(0,a,0)$. The edges of this triangle are uniformly charged with value $Q'$ and everything is in vacuum. I need to find the vector of ...
0
votes
0answers
32 views

Plank stopping time (Continuation and Physical meaning)

A while back I asked this problem: "Plank stopping time" I thought it was solved, but now I have some questions about the solution. Problem: A plank of length $L$ and mass $m$ lies on a ...
0
votes
3answers
74 views

What is the purpose of the factor $N/L$ in the magnetic field of a solenoid?

I am supposed to find the expression of the magnetic field on the axis of a solenoid of radius $a$, length $L$, and with $N$ the number of turns. So in order to find $dB$ (to integrate over dx), I ...
2
votes
0answers
100 views

Tension in a pulley system [closed]

In the question above, what I don't understand is how to calculate the tension in the second case (case in which the pulley is there). I realized after reading some questions, that the arrangement ...
0
votes
1answer
41 views

Derive the generating function for canonical transformation of type $F_3$

I'm working on some practice questions and I am a bit confused with this one: Generating functions of the type $F_1(q,Q)$ satisfy the condition: $$pdq-PdQ = dF_1$$ Starting from this condition ...
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votes
1answer
22 views

Voltage divider example [closed]

I have the following voltage divider circuit: Now, my goal is to find U_{L}. Altough, I know already the solution (U_{L}= ...
2
votes
1answer
38 views

When two plane mirror are inclined at 60° to each other?

How many images will be formed? In the case above I think 5 images will be form. But how can I exactly find out the number of images if the inclination angle is different. Is there any formula or it ...
0
votes
3answers
70 views

Damped simple harmonic oscillator problem

I'm supposed to calculate and draw the phase space trajectory for this: for the two different cases when and . I've never done this sort of question before, how are they done? I've tried ...
0
votes
1answer
39 views

Solving for current in a circuit problem (image included)

I need to find $I_{R_2}$ and I need someone to explain why $I_T = I_{R_1} = 1 mA$. I thought that we were supposed to use the fact that $I_T = I_{R_1} + I_{R_2} + I_{R_3}$: ! I have solved for $R_T ...